Blowing bubbles to make ships more fuel efficient

This is a screen shot from an video on how Dutch company Damen Shipyards Group has incorporated the concept of air lubrication to its ships.

Blowing a lot of bubbles under cargo ships turns out to be a good way to cut down on fuel costs, according to ongoing research on so-called air lubrication technology.

"The basic idea is that if you could somehow have air close to the hull, it would help the hull slip through the water better by reducing the skin friction," Steven Ceccio, a professor of naval architecture and mechanical engineering at the University of Michigan, explained to me Wednesday.

That works, he added, because air is about 1,000 times less dense than water, which has a corresponding reduction in friction around the hull.

"So the potential is really good," he said.

The caveat is that the air has to be pumped beneath the hull and kept there. The pumping takes energy and keeping it beneath the hull is a combination of physics and architecture.

In research over the past decade largely funded by the U.S. Navy, Ceccio has found if just a little air is pumped down, the bubbles just flow away and do little good.

"But if you get to a critical amount, if you put enough in, the bubbles coalesce together and they form a film and then it works really well," he said.

"It was one of those circumstances where half measures would not do the trick. You have to persevere, put a bunch of air in, and then things get better."

At least, things get better if the ship has a flat-bottomed hull, like most cargo ships. On V-shaped hulls, like those found on most Navy destroyers, "the bubbles may not form these layers and therefore your ability to lubricate with air is reduced," Ceccio noted.

Most recently, he applied air lubrication modeling to the typical type of flat-bottomed cargo ships that ply the Great Lakes region and found the technology could increase fuel efficiency by 5 to 20 percent.

Since fuel costs are often more than half of a cargo ship's total operating expenses, these types of savings could be huge, notes an Economist story on the technology.

John Roach is a contributing writer for msnbc.com. To learn more about him, check out his website. For more of our Future of Technology series, watch the featured video below.

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